1. Field of the Invention
This invention relates to a method of evaluating the catalytic activity of a rare earth alkoxide used as a starting material of a basic catalyst and an asymmetric synthesis catalyst.
2. Description of the Related Art
The rare earth alkoxide is a basic catalyst useful for organic synthesis and used in
Meerwein-Ponndorf-Verley-Oppenauer reaction (T. Okano: Quarterly Chemical Review, Organic Synthesis Using Lanthanoid (in Japanese), Gakkai Shuppan Center, No. 37, p. 130, (1998), edited by the Chemical Society of Japan). Further, Shibasaki et al. found that an La-Na-BINOL catalyst obtained by reacting a rare earth alkoxide, optically active BINOL and sodium tertiary butoxide, is useful for asymmetric Michel reaction (JP-A 8-291178) Similarly, an La-K-BINOL catalyst is useful for asymmetric hydrophosphonylation reaction (JP-A 8-325281), and an La-Li-BINOL catalyst is useful for a symmetric Mannich reaction (JP-A 10-120668).
It is empirically found that the catalytic performance thereof is influenced by the process and physical properties of the rare earth alkoxide, but the cause for the influence is not elucidated (T. Okano: Quarterly Chemical Review, organic Synthesis Using Lanthanoid (in Japanese), Gakkai Shuppan Center, No. 37, p. 130, (1998), edited by the Chemical Society of Japan), and in some cases, those rare earth alkoxides produced by the same synthesis method maybe different in the catalytic activity. For researchers and manufactures participating in synthesis using rare earth alkoxides, the supply of rare earth alkoxides of stable qualities is necessary, and a method of evaluating the catalytic activity of rare earth alkoxides has been desired for satisfying the supply.
However, there was none of literatures and patents describing the method of evaluating the catalytic activity of rare earth alkoxides.
Instrumental analysis by ICP-AES and H1-NMR, the present inventors analyzed those rare earth alkoxides which when used as catalyst materials, achieved a higher and lower activity respectively, but they could not found a difference in data therebetween.
Accordingly, the present inventors prepared catalysts from rare earth alkoxides as the starting material to be evaluated, and attempted at several kinds of asymmetric reactions in a scale of 100 ml or less, to determine the degree of conversion and enantiomeric excess, but asymmetric Michel reaction and asymmetric nitroaldol reaction were insensitive to the qualities of rare earth alkoxides, and the evaluation of the rare earth alkoxides by these reactions was difficult.